The invention pertains to a method of forming a compression coupling between the connecting piece of a fitting and a tube inserted into the retaining section of the fitting up to its mating edge, where a pressing tool is used in the region of an annular bulge of the fitting in which a sealing ring is seated.
The invention also pertains to a shaped part inserted into the retaining section of the fitting during implementation of the method.
It is known in the art to couple tubes together using cold deformation. Tubes to be coupled together generally have a retaining section at one end and a narrower section at the other, enabling one tube to be inserted into another. For the purpose of clarity, one tube will be called a fitting, and the other a tube.
Before the tube is inserted into the fitting, the sealing ring is installed in an interior, open retaining groove which is formed by a toroidal deformation of the fitting. After the insertion of the tube into the fitting, the sealing ring fits around and engages the exterior of the tube.
Frequently, the ends of tubes end have sharp edges, such as burrs formed during the manufacture or cutting of the tubes. These sharp edges expose the sealing ring to the risk of damage during insertion, which of course adversely affects the seal.
The invention addresses the problem the described above, so that upon insertion of a tube into a fitting, the sealing ring within the annular retaining groove will not be damaged by the sharp, outside edges on the leading end of the tube. Thus, when the parts to be joined are pressed together, the necessary tight seal will be achieved.
The invention addresses these problems existing in the prior art, in that before or during the insertion of the tube into the fitting, the sealing ring is elastically deformed from the inner contours by means of at least one engaged shaped part. The tube is inserted up to the mating edge and cold deformation is performed on the parts to be joined.
In the inventive method, one or more shaped parts are introduced into the retaining section of the fitting before, during or after insertion of the sealing ring, so that the sealing ring is forced away from the entry path of tube. Any sharp edges on the leading end of the tube which can possibly be part of an unremoved burr, cannot come into contact with the sealing ring.
Tubes that are joined with the fitting by means of cold deformation generally include metal tubing, which can be made of stainless steel or copper, for example. Plastic tubes and composite tubes are also possible; this method would work equally well with these and other tubes as well.
The shaped parts installed in the retaining section of the fitting or into the retaining groove of the sealing ring are preferably made of plastic. Different materials that satisfy the requirement are also possible.
The invention is a method of creating a compression coupling between a fitting and a tube. The fitting has a retaining region near an end portion of the fitting. The retaining region has an interior-oriented annular groove cooperatively formed with an exterior-oriented annular bulge on the retaining region. The tube has an end formed to fit into the retaining region of the fitting. The method comprising the steps of positioning a sealing ring in the groove, inserting a shaped part into the fitting to engage and radially outwardly deform the sealing ring to provide clearance between the sealing ring and the tube when the tube is installed into the fitting, installing the tube into the fitting, and pressing the retaining region onto the tube.
The method may also comprise the step of providing a shaped part that enters the groove to engage a middle region of the sealing ring. Additionally, the shaped part may comprise at least one of annular segments, casings, wedges, or stems.
In one embodiment, the shaped part is a casing formed to fit around the end of the tube and define a hollow interior. The casing has an inwardly-extending flange adjacent a first end and an outwardly-extending flange adjacent a second end, and a predetermined annular breaking region therebetween. The method using the casing involves the steps of inserting the end of the tube into the second end of the casing, and inserting the first end of casing into the fitting until the inwardly-extending flange engages an end of the tube and the outwardly extending flange engages an end of the fitting. The breaking region fails during this step, breaking the casing into two parts at the breaking region aligned with the sealing ring to form a separation by continued insertion. Preferably, the breaking region has a width that corresponds to the width of the sealing ring, and the sealing ring is pressed along all or part of entire width of the breaking region.
When the method is properly performed using the casing embodiment or any other embodiment, the seal elastically deforms during the pressing step such that approximately half of the sealing ring engages an exterior surface of the tube.
In another embodiment, the shaped part is formed to enter the groove and push the retaining ring into the groove and out of the interior of the retaining region.
In another embodiment, the shaping part comprises a ring shaped angular flange formed to engage a front surface of the fitting, and at least one segment extending inwardly from the annular flange. Each segment has a raised edge formed thereon adjacent an end distal the flange. A thin walled tongue is formed extending from each raised edge. Incorporating this embodiment into the claimed method, the raised edges engage a portion of the groove during the insertion step, and thin walled tongues extend approximately halfway past the sealing ring. In this embodiment, each annular segment will simultaneously engage the interior of the retaining region as well as the exterior of the tube during the installing step.
In another embodiment, the method may incorporate a shaping part comprising a ring shaped annular flange formed to engage a front surface of the fitting, and at least one stem formed so that an end of the stem engages an inner contour of the sealing ring during the inserting step. In this embodiment, the stem and the sealing ring are cooperatively formed so as to force the sealing ring into the groove during the inserting step and out of the path of the tube during the installing step.
In another embodiment, the method may incorporate a shaped part comprising a split ring having two legs, which in cross-section form an acute angle. A first leg is formed to engage an inner contour of the retaining ring, and a second leg will pass between the retaining ring and the groove. Preferably, the second leg may comprise annular segments.
In another embodiment, the method may incorporate a shaped part comprising a split clamping ring formed to installed within the groove, thereby pressing the sealing ring outwardly into the groove during the inserting step. Alternatively, the shaped part may comprise a split molded ring with an angular cross-section having a first leg braced against the sealing ring, and a second leg extending into an interior of the retaining region during the insertion step. In this embodiment, the second leg elastically deforms during the installing step.
In yet another embodiment, the method may include the step of inserting split rings within the groove so as to be positioned on both sides of the sealing ring.
The shaped part may be formed to have a predetermined break region defined by a thin, annular wall. The break region forms side contact surfaces which engage the sealing ring following the deformation that occurs during the pressing step. Specifically, the casing embodiment of the shaped part may comprise two parts that are joined together by the predetermined break region whose width corresponds to the width of the sealing ring. In another embodiment, the casing may comprise an outwardly protruding annular flange formed to engage an end of the fitting upon completion of the installment step.
Additionally, the annular flange may comprise a pin oriented in an axial direction. During the installing step, the pin is formed to engage the fitting upon the failure of the break region. Upon completion of the installing step, however, the pin bends radially outward.